Coaxial screw gear sleeve mechanism

ABSTRACT

An improved mechanism for expanding or lifting a device in accordance with various embodiments of the present invention is a coaxial screw gear sleeve mechanism. In various embodiments, coaxial screw gear sleeve mechanisms includes a post with a threaded exterior surface and a corresponding sleeve configured to surround the post, the corresponding sleeve having a threaded interior surface configured to interface with the threaded exterior surface of the post and a geared exterior surface. A drive mechanism can be configured to interface with the geared exterior surface of the sleeve, causing a device utilizing such a mechanism to expand or lift between a collapsed configuration and an expanded configuration.

RELATED APPLICATION

The present application claims the benefit of U.S. ProvisionalApplication No. 61/271,548, filed Jul. 22, 2009, and U.S. ProvisionalApplication No. 61/365,131, filed Jul. 16, 2010.

FIELD OF THE INVENTION

The present invention relates to mechanisms for expanding or liftingbetween a compressed configuration and an expanded configuration. Morespecifically, the present invention relates to a coaxial screw gearsleeve mechanism.

BACKGROUND OF THE INVENTION

Many devices use various mechanisms to expand or lift the device from acompressed configuration to an expanded configuration. The goal of suchmechanisms is typically to provide a device with the greatest differencebetween its compressed configuration and its expanded configuration,while still providing sufficient strength to provide a stable devicethat can support whatever type of load that may be placed on the device.However, many such mechanisms either require a large compressedconfiguration, limited expansion from the compressed configuration tothe expanded configuration, and/or lack the strength to keep the devicestable under loading conditions.

Accordingly, it would be desirable to provide a mechanism that can beused for expanding or lifting a device that provides for a smallcompressed configuration and a large expansion to an expandedconfiguration, while possessing sufficient strength to provide .a stablebase under loading conditions.

SUMMARY OF THE INVENTION

An improved mechanism for expanding or lifting a device in accordancewith various embodiments of the present invention is a coaxial screwgear sleeve mechanism. In various embodiments, coaxial screw gear sleevemechanism includes a post with a threaded exterior surface and acorresponding sleeve configured to surround the post, the correspondingsleeve having a threaded interior surface configured to interface withthe threaded exterior surface of the post and a geared exterior surface.A drive mechanism can be configured to interface with the gearedexterior surface of the sleeve, causing a device utilizing such amechanism to expand or lift between a collapsed configuration and anexpanded configuration.

In one embodiment, a coaxial screw gear sleeve mechanism includes a postwith a threaded exterior surface and a corresponding sleeve configuredto surround the post. The sleeve can have a threaded interior surfaceconfigured to interface with the threaded exterior surface of the postand a geared exterior surface. The device can further include a drivemechanism having a surface configured to interface with and drive thegeared exterior surface of the sleeve, which causes an expansion of thesleeve relative to the drive mechanism and the post relative to thesleeve.

In another embodiment, a method of expanding a jacking or liftingmechanism includes providing a coaxial screw gear sleeve mechanismincluding a threaded post, a corresponding sleeve having an interiorthread mating with the threaded post and an exterior gear mating with adrive mechanism. The mechanism is expanded or lifted from a collapsedconfiguration to an expanded configuration by operating the drivemechanism to rotate the sleeve relative to the post, therebysimultaneously expanding the sleeve relative to the drive mechanism andthe post relative to the sleeve.

The above summary of the various embodiments of the invention is notintended to describe each illustrated embodiment or every implementationof the invention. This summary represents, a simplified overview ofcertain aspects of the invention to facilitate a basic understanding ofthe invention and is not intended to identify key or critical elementsof the invention or delineate the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1A is perspective view of a device employing a coaxial screw gearsleeve mechanism according to an embodiment of the present invention ina collapsed configuration.

FIG. 1B is a perspective view of the device of FIG. 1A in an expandedconfiguration.

FIG. 1C is an exploded view of the device of FIG. 1A.

FIG. 1D is a partial sectional view of the device of FIG. 1A.

FIG. 2A is a partial side view of a coaxial screw gear sleeve mechanismaccording to an embodiment of the present invention.

FIG. 2B is a partial side view of the coaxial screw gear sleevemechanism of FIG. 2A.

FIG. 3A is a partial side view of a coaxial screw gear sleeve mechanismaccording to an embodiment of the present invention.

FIG. 3B is a partial side view of the coaxial screw gear sleevemechanism of FIG. 3A.

FIG. 4A is a partial top view of a coaxial screw gear sleeve mechanismaccording to an embodiment of the present invention.

FIG. 4B is a partial top view of the coaxial screw gear sleeve mechanismof FIG. 4A.

FIG. 5A is an end view of a device employing a coaxial screw gear sleevemechanism according to an embodiment of the present invention.

FIG. 5B is a cross-sectional end view of the device of FIG. 5A takenlooking into the page.

FIG. 6A is a front view of a device employing a coaxial screw gearsleeve mechanism according to an embodiment of the present invention.

FIG. 60 is a cross-sectional view of the device of FIG. 6A taken alongthe lines 6B-6B.

FIG. 7A is a front view of a a device employing a coaxial screw gearsleeve mechanism according to an embodiment of the present invention.

FIG. 7B is a cross-sectional view of the device of FIG. 7A taken alongthe lines 7B-7B.

FIG. 8A is an exploded view of a device employing a coaxial screw gearsleeve mechanism according to an embodiment of the present invention.

FIG. 8B is a perspective view of the device of FIG. 8A.

FIG. 8C is a front view of the device of FIG. 8A.

FIG. 8D is a cross-sectional view of the device of FIG. 8A taken alongthe lines 8D-8D in FIG. 8C.

FIG. 9A is an exploded view of a device employing a coaxial screw gearsleeve mechanism according to an embodiment of the present invention.

FIG. 9B is a perspective view of the device of FIG. 9A.

FIG. 9C is a bottom view of the device of FIG. 9A.

FIG. 9D is a cross-sectional view of the device of FIG. 9A taken alongthe lines 9D-9D in FIG. 9C.

FIG. 10A is a perspective view of a device employing a coaxial screwgear sleeve mechanism according to an embodiment of the presentinvention.

FIG. 10B is a front view of the device of FIG. 10A.

FIG. 10C is a cross-sectional view of the device of FIG. 10A taken alongthe lines 10C-10C in FIG. 10B.

FIG. 10D is a cross-sectional view of the device of FIG. 10A taken alongthe lines 10D-10D in FIG. 10B.

FIG. 11A is a perspective view of a device employing a coaxial screwgear sleeve mechanism according to an embodiment of the presentinvention.

FIG. 11B is a side view of the device of FIG. 11A.

FIG. 12A is a perspective view of a device employing a coaxial screwgear sleeve mechanism according to an embodiment of the presentinvention.

FIG. 12B is a side view of the device of FIG. 12A.

FIG. 13A is a perspective view of a device employing a coaxial screwgear sleeve mechanism according to an embodiment of the presentinvention.

FIG. 13B is a side view of the device of FIG. 13A.

FIG. 14A is a perspective view of an expandable device employing acoaxial screw gear sleeve mechanism according to an embodiment of thepresent invention.

FIG. 14B is a partial cutaway view of the device of FIG. 14A.

FIG. 15A is a perspective view of a expandable device employing acoaxial screw gear sleeve mechanism according to an embodiment of thepresent invention.

FIG. 15B is a partial view of the device of FIG. 15A.

FIG. 15C is a partial view of the device of FIG. 15A.

FIG. 15D is a partial view of the device of FIG. 15A.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, one skilled in the artwill recognize that the present invention may be practiced without thesespecific details. In other instances, well-known methods, procedures,and components have not been described in detail so as to notunnecessarily obscure aspects of the present invention.

Referring to FIGS. 1A-1C, there can be seen a device 100 that utilizes apair of coaxial screw gear sleeve mechanisms 101 according, to anembodiment of the present invention. FIG. 1A shows the device 100 andcoaxial screw gear sleeve mechanisms 101 in a fully compressedconfiguration, FIG. 1B shows a fully expanded configuration, and FIG. 1Cshows an exploded view of the device 100. Device 100 includes a firstmember 110 having an outer surface 102 and a second member 150 having anouter surface 104.

Device 100 can also include a pair of coaxial screw gear sleevemechanisms 101. Coaxial screw gear sleeve mechanisms 101 includerespective threaded post members 111, 112 extending from first member110 and a pair of threaded geared sleeves 120, 130 configured tosurround the post members 111, 112. Threaded post members 111, 112 canhave threads 113, 114 defined on an exterior surface thereof. Threadedgeared sleeves 120, 130 can have both interior threads 122, 132configured to interface with the threads 113, 114 of threaded postmembers 111, 112 and exterior threads 121, 131. In one embodiment, boththe exterior 121 and interior 122 threads of one of the sleeves 120 areof an opposite hand to the threads 131, 132 of the other sleeve 130.External threads 121, 131 of sleeves 120, 130 can have gear teeth 124,134 cut into the thread. In one embodiment, the gear teeth 124, 134 arenot cut down to the root, or minor diameter, of the threads 121, 131 inorder to maximize the strength of the threads. In the compressedconfiguration, threaded geared sleeves 120, 130 can fit within sleeveopenings 161, 162 in second member 150. Openings 161, 162 can includethreaded portions 151, 152 that mesh with exterior threads 121, 131 ofthreaded geared sleeves 120, 130. In some embodiments, as pictured,threaded geared sleeves 120, 130 can be substantially solid. In otherembodiments, threaded geared sleeves can include one or more slotsthrough the sleeve for mass reduction and material savings.

The coaxial screw gear sleeve mechanisms 101 can be actuated, and thedevice 100 therefore expanded, with the aid of a worm 140 that extendsthrough a worm aperture 154 in the device 100. The worm 140 can havefirst 142 and second 141 opposing threaded sections configured tointerface with the exterior threads having gear teeth 124, 134 ofthreaded geared sleeves 120, 130 through a pair of apertures 157, 158 inthreaded portions 151, 152 of sleeve openings 161, 162. The worm 140 caninclude a hex 143, 144 at each end of the worm 140 that allows it to bedriven by an external device.

A partial sectional view of a pair of coaxial screw gear sleevemechanisms 101 in use with a device 100 in FIG. 1D helps illustrate howa device can employ multiple coaxial screw gear sleeve mechanisms astelescoping mechanisms utilizing the threaded post members 111, 112,threaded geared sleeves 120, 130 and the worm 140 to expand the firstmember 110 and second member 150 relative to each other. By turning hex144 counterclockwise, and therefore the worm 140 counterclockwise, firstthreaded section 142 of worm 140 pulls the gear teeth 134 of threadedgeared sleeve 130 towards the hex head 144. This causes the sleeve 130to translate upward from the second member 150 and worm 140 alonginternal threads 152. As the sleeve 130 rotates while it translatesupward, the threaded post member 112 extending from the first member110, which is unable to turn, also translates upward with respect to thesleeve 130 and the second member 150. This second translation resultsfrom the opposite handed external threads 114 of the threaded postmember 112 being driven by the matching internal threads 132 of thesleeve 130. The same mechanics are occurring on the other side of thedevice with oppositely threaded sleeve 120 having external threads 121and internal threads 122, post member 111 having external threads 113and second threaded section 141 of worm 140.

Because the threads for like components for each device are oppositehanded, the threads 142 on one side of the worm 140 will be pulling thegear teeth 134 of the threaded geared'sleeve 130 while the threads 141on the other side of the worm MO will be pushing the gear teeth 124 onthe other sleeve 120, or vice versa depending on the direction ofrotation of the worm 140. These opposing forces applied to the worm 140by the threaded geared sleeves 120, 130 are carried in either tension orcompression by the worm 140.

Alternative drive mechanisms to worm drive for actuating coaxial screwgear sleeve mechanisms include piezoelectric actuators and any momentumimparting collision mechanism or configuration.

Referring now to FIGS. 2A and 2B, a preferred fit of gear teeth 124, 134of threaded geared sleeves 120; 130 with a cooperating thread such asinternal threaded portions, 151, 152 of second member 150 is shown. Asthe gear teeth 124, 134 are thrust towards the internal threads 151, 152of the second member 150 by the worm, the load between the gear teeth124, 134 and threads 151, 152 is balanced by the bearing surfaces 163,164 between the components, which results in the ability of the device100 to expand under or lift a substantial load. This fit between thegear teeth 124, 134 and the internal threads 151, 152 can be contrastwith the fit shown in FIGS. 3A and 3B. In those figures, when the gearteeth 124′, 134′ of the threaded geared sleeves 120′, 130′ are thrusttowards the internal threads 151′, 152′ of the second member 150′, theforce is not balanced by bearing surfaces as in FIG. 2B, but by theforce the internal threads 151′, 152′ apply to the gear teeth 124′,134′. This can result in the gear teeth 124′, 134′ acting as a wedge andbecoming jammed against the internal threads 151′, 152′, whichdramatically reduces the ability of the coaxial screw gear sleevemechanisms to expand under or lift substantial loads and makes themechanism more sensitive to friction between components. Optionally, aliquid or gas lubricant, such as silicon lubricant, may be used toreduce friction in the mechanism. Saline may also be used as alubricant.

It should be noted that although the threads depicted in the Figures areall screw threads in the form of projecting helical ribs, “thread” forthe purposes of the present invention can also refer to any othermechanism that translates rotational force into translational orlongitudinal movement. For example, in some embodiments threads can becomprised of a recirculating or spiral arrangement of bearings or anyother low friction arrangement, such as cooperating magnets.

In one embodiment, the height of a device 100 utilizing coaxial gearsleeve mechanisms 101 between the bearing surfaces 102, 104 in the fullycompressed configuration is 6.5 millimeters and the maximum fullyexpanded height is 12 millimeters, thus providing a very large amount ofexpansion relative to the initial height of the device. The maximumheight is defined by the largest height at which the device can meet thedynamic compressive, shear, and torsional requirements for the given useof the device. Variables that determine this height include the width ofthe threaded geared sleeves, which is limited by the desired width ofthe device, and the material from which the device is made. With regardto the material for the device, materials with higher fatigueperformance allow the maximum height of the device to be taller evenwith a narrower width.

Once expanded, coaxial gear sleeve mechanisms 101 do not require alocking mechanism to maintain the desired height, even under loadingconditions. This is because, when driven backwards, the mechanismexhibits a very high gear ratio which causes even the slightest frictionin the system to overwhelm any amount of compression, torsion, or shearloading that might be applied to the device. In dynamic testing inshear, torsion, and compression, the maximum amount by which the heightof one embodiment of the device that had a maximum expansion of 5.5millimeters changed was by approximately 0.01 millimeter. The device100, because height can be maintained at any point along the threadedgeared sleeves, therefore also exhibits very high resolution heightcontrol, on the order oft micrometer.

In one embodiment, the external threads 121, 131 and gear teeth 124, 134on the threaded geared sleeves 120, 130 can be substantially trapezoidalin shape. In one embodiment, the thread is a trapezoidal 8 millimeter by1.5 millimeter metric thread. A trapezoidal design enables a relativelylarge gear tooth size and, accordingly, a larger area over which theexpansion or lifting loading is distributed. Additionally, with precisemanufacturing, multiple gear teeth 124, 134 on the threaded gearedsleeves 120, 130 can be engaged by the worm 140 at the same time alongthe pressure angle ANG, as shown in FIGS. 4A and 4B. Distributing theexpansion load over multiple teeth of the sleeves 120, 130 and the worm140 is critical to achieve the minimum device size while providing amaximum amount of expansion or lift and load capacity. In oneembodiment, the coaxial gear sleeve mechanisms 101 can be used with adevice 100 having a. strengthened second member 150 as shown in FIGS. 5Aand 5B. This can be done by lowering the worm aperture 154, andtherefore the worm 140, such that when the device 100 is expanded to itsfull height, the worm 140 engages a MI gear tooth 134A on the threadedgeared sleeve 130 closest to the bottom 136 of the threaded gearedsleeve 130. This allows a top surface 166 of the second member 150 to belowered, which allows the first member 110 to be thicker, and thereforestronger, while maintaining the same initial height In addition, thisallows the material 168 between the top surface 166 of the second member150 and the worm aperture 154 to be made thicker. A further advantage ofthis configuration is that at least one full internal thread 152A of thesecond member 150 is in engagement with the threaded geared sleeve 134when the device is fully expanded. In such a configuration, anadditional thickness 167 can be added to the side of second member 150opposite of the worm aperture 154 to what was previously described asthe top surface 166A of that side of the second member 150. This allowsfor a full internal thread 152B to engage the threaded geared sleeve 130on the side opposite of internal thread 152A. By capturing the threadedgeared sleeve with a full thread on both sides, when the device isloaded with shear and torsion, a maximum amount of material is resistingthe load, which minimizes the resulting stress and increases the fatiguelife of the device 100.

FIGS. 6A and 6B depict another embodiment of the present invention wherein threaded posts 111, 112 employ a buttress thread 113A, 114A (comparethreads 113A in FIG. 6B to threads 113, 114 in FIG. 1D). A buttressthread configuration results in the load bearing thread face beingperpendicular to the screw axis of the post 111, 112, which increasesthe axial strength of the coaxial screw gear sleeve mechanisms. FIGS. 7Aand 7B depict a further embodiment that utilizes a standard 60 degreethread 113B, 114B on threaded posts 111, 112. 60 degree threads areconsidered industry standard and can therefore be created with commonmachining practices. This can result in a device that can be morequickly and inexpensively produced.

Referring now to FIGS. 8A-8D, another expandable device 400 includes apair of coaxial screw gear sleeve mechanisms 401 comprising threadedgeared posts 423 extending between first member 410 and second member450 rather than the separate threaded geared sleeves 120, 130 andthreaded posts 111,112 described previously. Threaded geared posts 423each include a threaded geared portion 421 and a post portion 411.Threaded geared portions 421 fit within openings 461 in second member450 and interface with worm 440 and internal threads 451 to cause thedevice 400 to expand or lift. Post portions 411 fit within openings 416in first member 410 and can be attached to washers 418. Washers 418 keepthe first member 410 in place relative to the threaded geared posts 423as the threaded geared posts 423 rotate freely independent of the firstmember 410 when the device 400 is actuated. Thus, as seen in FIGS. 8Cand 8D, the expansion between the first member 410 and the second member450 is caused by the thicker threaded geared portions 421 while the postportions 411 remain within the openings 416 in first member 410. Thisleads to a device 400 having increased axial strength.

FIGS. 9A-9D depict a further embodiment of an expandable device 500utilizing coaxial screw gear sleeve mechanisms 501 that allows fordifferential adjustment of the threaded geared sleeves 520. Threadedposts 511 can each include an arched portion 515 that corresponds to anarched recess 517 in first member 510. The arched interface between thethreaded posts 511 and the first member 510 created by the correspondingarched portions 515 and arched recesses 517 allows the first member 510to rotate and become angled relative to the second member 550. A pinjoint utilizing a pivot pin 572 can be used to keep one interfacebetween the first member 510 and a threaded post 511 stationary, whilethe other interface is allowed to slide due to the arched surfaces. Aplacement pin 570 is used to prevent the worm 540 from sliding out ofthe second member 550 when expanding the device. Worm 540 can be atwo-part worm including a first portion 546 having a first threadedsection 543 and second portion 548 having a second threaded section 544that fits onto a post 547 of first portion 546. The two portions 546,548 can therefore be rotated independently of each other, with eachdriving a separate threaded geared sleeve 520. Because each threadedgeared sleeve 520 can be engaged separately, they can be expanded bydifferent amounts, resulting in an angled first member 510 as shown mostclearly in FIG. 9D. Optionally, the arched recesses 517 in the firstmember 550 and arched surfaces 515 of the posts 511 could be replacedwith flexural joints or ball or cylinder and socket joints.

An expandable device 600 according to another embodiment of the presentinvention is depicted in FIGS. 10A-10D. Device 600 uses three coaxialscrew gear sleeve mechanisms 601, each having a threaded geared sleeve620 and a threaded post 621, between first member 610 and second member650. As seen in FIGS. 10C and 10D, to expand or lift the device, theworm drive 640 is rotated and it engages one of the threaded gearedsleeves 620, causing it to rotate. As the first threaded geared sleeve620 rotates; it engages the other two threaded geared sleeves 620,causing them to rotate and the device 600 to expand. The rotation of thethreaded geared sleeves 620 also causes the threaded posts 621 toexpand, as described previously. Use of three coaxial screw gear sleevemechanisms provides for a device having increased strength in the axialdirection and a broader surface area for supporting loads. Optionally,each of the three expansion mechanisms could be actuated independentlyto adjust the surface of the device in additional degrees of freedom.

FIGS. 11A and 11B depict a device 700 that employs only a single coaxialscrew gear mechanism 701 having a threaded geared sleeve 720 and athreaded post 721 for expanding first member 710 relative to secondmember 750 with worm 740. Device 700 also can include first 774 andsecond 776 telescoping support elements. Telescoping support elements774, 776 serve to maintain the relative rotational positioning of thefirst member 710 with respect to the second member 750, enabling thethreaded geared sleeve 720 to rotate with respect to both the firstmember 710 and second member 750 to expand the device 700. FIGS. 12A and12B depict a further variation of device 700 that utilizes a pluralityof spikes 778 extending from the first member 710 and second member 750to rotationally constrain the first member 710 and second member 750. Inoperation, the spikes 778 contact adjacent surfaces and can fixthemselves to those surfaces to prevent the first member 710 and secondmember 750 from rotating relative to each other. A further embodiment isdepicted in FIGS. 13A and 13B. This embodiment includes a coaxial screwgear sleeve mechanism having only a threaded geared sleeve 720 betweenfirst member 710 and second member 750 and allows the first member 710to rotate with the sleeve 720 as the device 700 is expanded via rotationof the worm 740. Optionally, first member 710 could be rotationally freewith respect to the threaded geared sleeve 720 so that the first member710 is allowed to engage and not rotate against an adjacent surface.

FIGS. 14A and 14B depict an expandable device 800 including anenveloping coaxial screw gear sleeve with recirculating bearingsaccording to another embodiment of the present invention. Device 800includes a post 810, an enveloping coaxial screw gear sleeve 820, a worm830 and a housing 840. Post 810 includes a smooth outer surface 812 anda machined helical raceway 811 for bearings 813. A helical raceway (notshown) is also machined into inner surface of enveloping coaxial screwgear sleeve 820 that is complementary to helical raceway 811 foraccommodating bearings 813. The inner surface of coaxial screw gearsleeve 820 also includes a machined tunnel for recirculation of bearings813 as the post 810 moves with respect to the sleeve 820. Therecirculating bearings are depicted as bearings 814 in FIG. 14B. Theouter surface of the enveloping coaxial screw gear sleeve also includesa helical raceway 821 for recirculating bearings 814 and an envelopingscrew gear 822. The worm 830 has a helical thread configured to engagethe enveloping screw gear 822 of the sleeve 820. The inner surface ofthe housing 840 has a helical raceway (not shown) that cooperates withhelical raceway 821 to retain bearings 814 and a tunnel forrecirculating bearings 814 as the coaxial screw gear sleeve 820 moveswith respect to the housing 840.

To expand the device 800, the worm 830 is rotated clockwise to engagethe enveloping screw gear 822 to rotate and translate the envelopingcoaxial screw gear sleeve 820 out of the housing 840. Thissimultaneously causes the post 810 to translate (but not rotate) out ofthe enveloping coaxial screw gear sleeve 820 and away from the housing840. Bearings 813, 814 enable the rotation of the enveloping coaxialscrew gear sleeve 820 with very little friction, enabling the device 800to exhibit a very high mechanical advantage and displacement controlwith very high resolution. The use of the enveloping screw gear 822enables the interface between the worm 830 and the enveloping coaxialscrew gear sleeve 820 to carry substantially higher loading. Referringnow to FIGS. 15A-15D, there can be seen another expandable device 900utilizing a coaxial screw gear sleeve according to an embodiment of thepresent invention. Device 900 includes an enveloping coaxial screw gear910, a housing 920 and a worm 930. The outer surface of envelopingcoaxial screw gear sleeve 910 includes a helical groove having a seriesof enveloping coaxial screw gear teeth 914. The helical groove cancooperate with an internal thread 921 on the inner surface 922 ofhousing 920 to allow the device 900 to carry an axial load. In anotherembodiment, the gear teeth 914 can be machined directly into the outersurface of the enveloping coaxial screw gear sleeve 910. In oneembodiment, the outer surface of the enveloping coaxial screw gearsleeve 910 can be a smooth machined surface that acts like a bearingsurface when configured with a similar smooth bearing surface on theinner surface 922 of housing 920 to enable the device 900 to carry alateral load. Optionally, the coaxial screw gear sleeve 920 could haverecirculating, bearings both on the inside and the outside of the sleeveand the recirculation tunnel could be between the inside and the outsideof the sleeve, both facilitating assembly and manufacturing.

To expand the device 900, the worm 930 is rotated to engage theenveloping coaxial screw gear teeth 914 to rotate and translate theenveloping coaxial screw gear sleeve 910 with respect to the housing920. In one embodiment, the inner surface 910 and center bore 912 can beconfigured to contain a post similar to the post 910 described in FIGS.14A and 14B to compound the expansion or lift of the device. In oneembodiment, no thread 921 is present on the inner surface 922 of housing920, so the helical groove and/or gear teeth 914 of the envelopingcoxial screw gear sleeve 910 cause the sleeve 910 to translate withrespect to the housing 930 as the sleeve 910 rotates. In such aconfiguration, the worm 930 would carry any axial load, unassisted by aninclined interface between the enveloping coaxial screw gear sleeve 910and the housing 920.

Coaxial screw gear sleeve mechanisms as described herein can be made outof any material, including metals, plastics and ceramics. In oneembodiment, coaxial screw gear sleeve mechanisms as described herein canbe made of titanium. In other embodiments mechanisms can be made fromcobalt chrome, MP35N, PEEK, stainless steel, or carbon fiber.

Coaxial screw gear sleeve mechanisms can be manufactured in variousways. In one embodiment, thread milling can be implemented tomanufacture the various threads in device. Wire EDM can be utilized tomanufacture some or all of the holes and openings in the device.Assembly jigs and post processing steps can also be utilized to allowthe device to be manufactured to exacting standards.

Various embodiments of systems, devices, and methods have been describedherein. These embodiments are given only by way of example and are notintended to limit the scope of the present invention. It should beappreciated, moreover, that the various features of the embodiments thathave been described may be combined in various ways to produce numerousadditional embodiments. Moreover, while various materials, dimensions,shapes, implantation locations, etc. have been described for use withdisclosed embodiments, others besides those disclosed may be utilizedwithout exceeding the scope of the invention.

1. (canceled)
 2. A method comprising: placing a lifting device in aretracted state in which a first member of the lifting device isadjacent a second member of the lifting device; and rotating a firstsleeve rotatably coupled to the first member, which, in turn,non-rotatably translates a first post extending from the second member,thereby transitioning the lifting device to an expanded state in whichthe first and second members are spaced apart.
 3. The method accordingto claim 2, wherein rotating the first sleeve includes axiallytranslating the first sleeve relative to the first member simultaneouslywith the first post translating relative to the first sleeve.
 4. Themethod according to claim 2, wherein rotating the first sleeve includesthe first sleeve surrounding the first post.
 5. The method according toclaim 4, wherein rotating the first sleeve includes the first posthaving a threaded exterior surface threadably engaging a threadedinterior surface of the first sleeve.
 6. The method according to claim2, wherein rotating the first sleeve includes the first sleeve having ahelically geared exterior surface.
 7. The method according to claim 6,wherein rotating the first sleeve includes actuating a drive mechanismhaving a surface configured to interface with the helically gearedexterior surface of the first sleeve.
 8. The method according to claim6, wherein rotating the first sleeve includes rotating a worm drivehaving a threaded section operatively engaging the helically gearedexterior surface of the first sleeve.
 9. The method according to claim8, wherein rotating the first sleeve includes the worm drive rotatablydisposed in the first member, the first member having a unitary body.10. The method according to claim 2, wherein placing the lifting devicein the retracted state includes the lifting device having the first andsecond members having lengths greater than a height of the liftingdevice when the lifting device in the retracted state.
 11. A methodcomprising: positioning a lifting device including first and secondmembers and a size-adjustable support configured to transition the firstand second members between retracted and expanded states, the secondmember having first and second posts; and actuating a drive mechanismconfigured to interface with first and second sleeves of thesize-adjustable support, the first and second sleeves operativelyengaging the first member such that actuation of the drive mechanismtelescopically expands the size-adjustable support with respect to thefirst member, which axially translates the first and second sleevesrelative to the first member while the first and second posts translaterelative to the respective first and second sleeves.
 12. The methodaccording to claim 11, wherein positioning the lifting device includesthe second member having at least one post of the first or second postsbeing non- rotatable.
 13. The method according to claim 11, whereinactuating the drive mechanism includes extending at least a portion ofthe first or second sleeves out of the first member.
 14. The methodaccording to claim 11, wherein actuating the drive mechanism includesthe drive mechanism having a surface configured to interface with anddrive helically geared exterior surfaces of the first and secondsleeves.
 15. The method according to claim 11, wherein actuating thedrive mechanism includes the first sleeve configured to surround thefirst post or rotating the second sleeve configured to surround thesecond post.
 16. The method according to claim 11, wherein actuating thedrive mechanism includes rotating the first sleeve rotatably coupled tothe first member, which, in turn, non-rotatably translates the firstpost extending from the second member, thereby transitioning the liftingdevice to an expanded state in which the first and second members arespaced apart.
 17. The method according to claim 11, wherein actuatingthe drive mechanism includes the drive mechanism including a worm drivehaving a pair of threaded sections, each threaded section configured tointerface with only one of the first and second sleeves.
 18. The methodaccording to claim 11, wherein actuating the drive mechanism includestranslating the first post having a threaded exterior surface engaging athreaded interior surface of the first sleeve.
 19. The method accordingto claim 11, wherein positioning the lifting device includes the liftingdevice having the size-adjustable support movable relative to the firstmember between a first position, in which, the size-adjustable supportengages the first member, and a second position, in which, thesize-adjustable support is spaced apart from the first member.
 20. Themethod according to claim 11, further comprising placing the liftingdevice between adjacent structures.
 21. The method according to claim11, further comprising placing the lifting device between two surfaces.